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Old 03-24-2013, 02:41 AM   #1
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Basement Insulation Planning Questions

A little back ground on my situation and my project. I am in Virginia Zone 4, which requires R-10 continuous in basements. House built in 2008, my big DIY project actually. All walls are cinder block with no insulation on outside, or under slab, cut costs at the time by not doing it, big mistake. Everything is sealed up pretty well though, have not had any water issues. I installed HVAC ducts, and an air return on the floor, so heat and AC are already there.

I would like to run through what I have and ask for advice please. And I have read Building Science recomendations. Read a ton for years now, been planning to do this since I built the house.

1. Back wall is full daylight walkout with french doors. Is XPS needed, or can I just frame out with 2X4 and fill with unfaced batts? If I use XPS can I just use 2" and no batts with 2X4 (want to run electric in walls)? Will leaving wall cavities empty cause problems?

2. Long wall beside of attached garage is against 400 tons of gravel, had to back fill entire garage to build up to grade. Is 2" XPS really needed here? If so again can I leave cavities empty?

3. Opposite long wall is 3/4 above grade. Again XPS 2" with empty cavities acceptable?

4. This is the one that really has me stumped. Under front porch is a cold room. Put in an exterior steel door, and leave it closed off, it is definitely cold. If I insulate this wall to separate from the rest of the basement do I still use 2" XPS? The problem also is I am starting to get mold in the cold room. I framed the front porch with treated plywood, and poured concrete over it. Roughly 8" thick. The mold is growing on the treated plywood. Should I try and remove this treated plywood? Not sure how to cut it out. Maybe install a dehumidifier? I think I am getting some warm air from the conditioned basement, causing the mold. I also thought about just insulating it also, make it useable for something besides storing fruit and veggies.

5. The floor is cold. I did not install any foam under the slab. Since I want this to be comfortable living space, theater, bar, weight room, should I insulate? I have plenty of head room, unfinished ceiling height right now is 9', I added a couple of extra courses of block for this very purpose. I was thinking 1" XPS on floor would be plenty, than finish with laminate, or cork, rubber mats for workout area. But code does call for R-10.

In closing, hoping this might generate some discussion. I am not in a rush to complete, built this house for the long haul. I have some pictures I took if it helps, and I can figure out how to post them I can. Thanks in advance for reading.


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Old 03-26-2013, 04:22 PM   #2
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Where in Virginia? Closest city listed below the map:

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Old 03-27-2013, 04:57 AM   #3
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All of Va is 4A

It says all of Virginia is 4A.
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Old 03-27-2013, 08:01 AM   #4
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If you are doing it once, I prefer the idea of XPS. While R-Value is R-Value, some instances and applications just work better.

Spend the money once and be happy that you did.

As far as the cold room goes, it is likely that there is some humidity from the home making it in there of ground humidity perking up.

A foam thermal break across the floor would do wonders to warm it up as well.
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